1. Field of the Invention
The present invention relates to devices for reducing material into uniform small size pieces.
2. Prior Art
The problems in shredding polymers, elastomers, and similar materials are well known. One of the items that is the most difficult to dispose of still comprises the automobile tire which is a tough elastomeric material. Many land fill operations will not take tires, and while the elastomer forming the tire is valuable as a fuel, a full size tire cannot be burned in most furnaces. Shredding a tire is an extremely difficult proposition because of the resiliency, toughness, and general resistance to any type of cutting action of the ordinary vehicle tire.
Prior art devices for chopping polymers, and shredding other materials have been advanced. A type of knife used on a rotor, cooperating with a bed knife for chopping material such as plastic is shown in U.S. Pat. No. 3,779,123. A sawtooth type design is incorporated, and with such sawtooth design, in a uniform infeed, strips of material are removed, rather than small uniform pieces which find utilization in automatic feeders for furnaces or the like. A similar device is shown in U.S. Pat. No. 3,545,686, and another sawtooth design which is specifically utilized in a two step cut is shown in U.S. Pat. No. 3,762,256. Again the sawtooth edges shown in these mentioned patents will result in a strip being removed from the material to be shredded or chopped up, and will not accomplish the results of producing a uniform size piece of material that is of small enough size so that it can be used in furnaces or the like for generating power.
Other rotating devices that are used for chopping materials are shown in U.S. Pat. No. 3,658,256, which shows knives which work against a sawtooth bed, and U.S. Pat. No. 3,602,445 which is used for propelling material against a impact surface for shredding.